Synergistic application of thermally-pretreated-biocatalyst and dark-fermentative process coupled with bioelectrohydrogenesis promotes biohydrogen production from agricultural straw wastes

Abstract

This work investigated the feasibility of enhancing biohydrogen yield from agricultural wheat straw by introducing an electrohydrogenesis process into dark fermentation (DF) and using heat-pretreated activated sludge as inoculum as a strategy to inhibit the methanogens’ growth. The achieved maximum biohydrogen yield was 5.416 mmol H2/g-straw with an energy recovery efficiency of 94.4 %. It reported a maximum coulombic efficiency of 74 % and chemical oxygen demand (COD) removal efficiency of 81.32 % whereas the maximum NH3-H removal efficiency was 42.25 %. The main volatile fatty acids (VFA) detected at the end of DF were acetic acid, propionic acid, and butyric acid, respectively, reduced by 84.07 %, 77.38 %, and 75.52 % at the end of the second phase of electrohydrogenesis. Moreover, this novel strategy promoted the conversion of lignocellulosic components compared to the non-pretreated activated sludge-catalyzed fermentative bioreactors, where the cellulose, lignin, and hemicellulose removal rates rose by 58.4 %, 55.5 %, and 79.5 %, respectively. These results revealed that coupling the electrohydrogenesis with dark fermentation in the process biocatalyzed by a thermally-pretreated activated sludge remarkably inhibited methanogen growth and improved the biohydrogen yield from agricultural straw residues. Hence, this investigation provides a novel technology utilizing agricultural straw biomass as a bioresource other than waste.

Keywords

• Biohydrogen energy
• Dark fermentation
• Agricultural straw wastes
• Microbial electrolysis cells
• Thermally-pretreated inoculum